A suggestion for modules names / sharing code between projects

[Mike Parker via Digitalmars-d]

On Monday, 29 February 2016 at 21:43:31 UTC, Sebastien Alaiwan 
wrote:

>>> Ok so now let's say I rename the directory "lib" to "foo". If 
>>> I don't change the "import lib.hello" to "import foo.hello", 
>>> how is the compiler going to find "hello.d"?
>>
>> You have to tell the compiler where it is.
> Is it only possible with separate compilation?


Given two modules, src/lib/foo.d and and src/main.d, you can pass 
them both to the command line and not worry about passing -I to 
the compiler.

dmd src/main.d src/lib/foo.d

In this case, foo.d can have a module statement that gives it any 
name at all. It does not need to match its directory structure:

module wicked.cool.mod;

This works because you've given the module directly to the 
compiler and it doesn't need to search for it. If you compile 
them separately:

dmd -c src/lib/foo.d
dmd src/main.d foo.obj

Now you will see a compiler error. You've given the compiler 
foo's object file, but it doesn't know where the source file is. 
When main.d imported wicked.foo.mod, the compiler tried to find 
wicked/foo/mod.d from its current working directory. No joy. You 
can test this changing the module declaration in foo.d to 
lib.foo, then importing lib.foo in main.d. The you can do this:

cd src
dmd -c lib/foo.d
dmd main.d foo.obj

Now when it encounters import lib.foo, it will look for lib/foo.d 
and find it. Now do this:

cd ..
dmd -c src/lib/foo.d
dmd src/main.d foo.obj

Again, failure, because it's looking for lib/foo.d. So now you 
have to tell it where to find lib/foo.d:

dmd -Isrc src/main.d foo.obj

Now it will look for src/lib/foo.d and find it.

This is why you shouldn't muck about with package names. If you 
want to change the name of the src directory, that's fine. You 
can simply pass -I to the compiler with the correct value. But if 
you want to change the name of lib, you are now affecting the 
compiler's ability to find imports. This becomes a problem with 
separate compilation (as above), which also means it's a problem 
when using libraries. If you change a package name for something 
you're distributing as a library, then all the import statements 
in client code will need to be changed as well.